本文關鍵詞： 腐蝕 螺桿鉆具 硬鉻鍍層 氯離子 正交實驗法 動電位掃描　出處：《重慶科技學院》2017年碩士論文　論文類型：學位論文

【摘要】：隨著我國油氣開發(fā)行業(yè)的進一步發(fā)展和井下油氣鉆井技術的逐漸成熟,螺桿鉆具常被廣泛應用到定向井和水平井的鉆井過程中。然而,根據(jù)油氣田的現(xiàn)場應用表明,鹽水鉆井液常被用在鉆井過程中,致使螺旋鉆桿表面硬鉻鍍層發(fā)生嚴重的腐蝕。嚴重的腐蝕將縮短螺桿鉆具使用壽命,直接導致經(jīng)濟成本的增加,還可能造成事故風險增加,甚至有人員傷害的可能。目前,國內(nèi)外學者研究氯離子腐蝕的課題較多,但是針對螺桿鉆具在鹽水鉆井液工況中腐蝕行為的系統(tǒng)研究較少,制造企業(yè)也缺乏充分的參考依據(jù)。因此研究實際工況下螺桿鉆具硬鉻鍍層的腐蝕規(guī)律具有重要的學術價值和工程應用意義。本文通過收集目前螺桿鉆具在井下工作的工況信息,擬定了基本工況條件參數(shù),即溫度、壓力和氯離子濃度,以及各參數(shù)的范圍。利用高溫高壓反應釜模擬螺桿鉆具在井下的基本工況條件,對螺桿鉆具表面硬鉻鍍層進行腐蝕和檢測,并以常溫常壓環(huán)境鍍鉻層的腐蝕試驗以及電化學參數(shù)作為參考,通過正交實驗法研究溫度、壓力和氯離子濃度對硬鉻鍍層腐蝕的影響,采用開路電位、動電位掃描和失重腐蝕法研究硬鉻鍍層的電化學參數(shù)及腐蝕特征,采用掃描電子顯微鏡和能譜觀察和分析鍍層腐蝕前后的微觀形貌和表面成分。研究發(fā)現(xiàn),鍍層的腐蝕速率隨著氯離子濃度的升高而降低,隨著溫度的升高而升高,隨著壓力的升高而升高。影響硬鉻鍍層腐蝕速率最大的因素是氯離子濃度的變化,其次是溫度,再次是壓力。從基本工況條件可以推斷硬鉻鍍層腐蝕最嚴重的情況是在溫度為180℃、壓力為15MPa和氯離子濃度為30g/L的參數(shù)附近。從鍍層腐蝕前后形貌看,氯離子優(yōu)先在敏感位置(鈍化膜的薄弱點處)引發(fā)孔蝕核,在閉塞腐蝕電池催化作用下,鍍層表面不斷形成孔蝕,腐蝕孔加大形成宏觀腐蝕坑;同時裂紋處受到一定程度的腐蝕,裂紋被明顯加寬;個別嚴重的情況下,腐蝕導致少部分區(qū)域鍍層深孔、剝落,甚至穿透鍍層,形成陰極鍍層與基體之間的電偶腐蝕。
[Abstract]:With the further development of China's oil and gas development industry and the maturation of downhole oil and gas drilling technology, screw drilling tools are often widely used in the drilling process of directional wells and horizontal wells. However, according to the field application of oil and gas fields, Salt water drilling fluid is often used in drilling process, which results in serious corrosion of hard chromium coating on helical drill pipe surface. Serious corrosion will shorten the service life of screw drill pipe, directly lead to the increase of economic cost, and may also increase the risk of accident. There is even the possibility of human injury. At present, scholars at home and abroad study more topics of chloride ion corrosion, but there are few systematic studies on corrosion behavior of screw drilling tools in brine drilling fluid. Therefore, it has important academic value and engineering application significance to study the corrosion law of hard chromium coating of screw drill tool under actual working condition. The basic operating condition parameters, that is, temperature, pressure and chloride concentration, and the range of the parameters are worked out. The basic working conditions of the screw drilling tool are simulated by using a high temperature and high pressure reactor. The corrosion and detection of hard chromium coating on the surface of screw drill tool were carried out. The corrosion test and electrochemical parameters of chromium plating layer in normal temperature and atmospheric pressure were used as reference, and the temperature was studied by orthogonal test method. The effect of pressure and chloride concentration on the corrosion of hard chromium coating was studied. The electrochemical parameters and corrosion characteristics of hard chromium coating were studied by open-circuit potential, potentiodynamic scanning and weightlessness corrosion. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to observe and analyze the microstructure and surface composition of the coating before and after corrosion. It was found that the corrosion rate of the coating decreased with the increase of chloride concentration and increased with the increase of temperature. The corrosion rate of hard chromium coating increased with the increase of pressure. The change of chloride concentration was the most important factor, followed by temperature. From the basic operating conditions, we can infer that the most serious corrosion of hard chromium coating is near the temperature of 180 鈩，

本文編號：1502686